officials struggle to communicate with a skeptical public, they face a radically changed social media environment where youtube videos spread virally across the internet. >> a regular flu shot gone horribly wrong. >> these people were much more likely to believe something they had seen on youtube than the centers for disease control and the fda. that's a little frightening. >> tonight, frontline reports on the science and politics of the bitter "vaccine war." >> frontline is made possible by contributions to your pbs station from viewers like you. thank you.and by the corporatir public broadcasting. major funding is provided by the john d. and catherine t. macarthur foundation, committed to building a more just, verdant, and peaceful world. and by reva and david logan, committed to investigative journalism as the guardian of the public interest. additional funding is provided by the park foundation, dedicated to heightening public awareness of critical issues. and by the frontline journalism fund. with grants from scott nathan and laura debonis, and the hagler family. >> what a cute little face.